If too few prizes are being won here's some of the causes

Ensure hard grab is working on a recurring basis - run coins through it until you see the voltage meter needle go right to its limit and catch the prize on hard grab before it goes past the sensor. Ensure that the hard grab is strong enough to hold on to that particular prize. If not, you may need to put rubber fingers on.

Ensure hard grab is working on a continuous basis by checking dipswitch settings are correct

Ensure frequency setting is correct. Standard. LCM.

New machines require about $1000 dollars to be accumulated so that the machine can do its calculations